1. Field of the Invention
The present invention relates to a zoom lens and an image pickup apparatus. The present invention relates to a zoom lens and an image pickup apparatus for a charge-coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) that are used for a digital camera or a video camera for example, that have a variable power ratio of about 5 to 7 and a field angle of at a wide angle end equal to or higher than 60°, and that can reduce the thickness of the camera.
2. Description of Related Art
A digital still camera or a video camera using a CCD or a CMOS highly requires a type of a lens by which the thickness of the camera can be reduced in particular. Recently, such a camera also requires a more sophisticated optical specification such as a further higher variable power ratio. A kind of a camera having a thin thickness frequently uses a bending optical system that bends an optical axis by 90 degrees by a reflective optical element (e.g., prism). This is disclosed, for example, in Japanese Patent Laid-Open Publication No. 2005-91465 and Japanese Patent Laid-Open Publication No. 2005-195757 for example.
However, in these zoom lenses according to the prior art using the bending optical system, a 5 group configuration uses a variable power ratio of about 4 and a 6 group configuration uses a variable power ratio of about 5. Thus, it has been difficult to provide a sufficient variable power ratio to the number of lens groups in the configuration.